I did this upgrade several times on an old box when W10 first came out. I had several BSDs which were all (?) related to the video 'card'. W10 dropped support for many old video cards.

I usually got it going by dropping to lower resolution which involved 'safemode' or equivalent - I can't remember but it involved numerous reboots and was quite different to W7. Eventually I bought a newer video card from CeX for £20.

MS publish a program that checks the hardware for compatibility. I had run that but it didn't identify this video card as a problem.

You'd be better off with a clean install, but I assume you don't want to overwrite W7. Get another HD?